• 수산해양기술연구
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• 제21권2호
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• pp.151-156
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• 1985

본 연구에서는 양쪽크랙 인장시험편을 이용한 평면응력 파괴인성치 J 하(1C)를 검토하기 위하여, 두께 4.5mm 일반구조용 압연강판(SS41)을 균질화 및 연화처리하고 각각의 경우에 대하여 크랙비가 0.55, 0.65, 0.75인 시험편을 준비하여 J 하(1C) 및 저항곡선의 거동을 고찰하였다. 얻어진 결과를 요약하면 다음과 같다. 1) 양쪽 크랙 인장시험편을 사용하여 J 하(1C)를 구한 값은 한계하중에 의한 방법이 Rice가 제안한 방법보다 크게 나타남을 알 수 있다. 2) Rice가 제안한 방법으로 J 하(1C)는 실험한 크랙비 범위 0.55-0.75에서 거의 일정한 값을 나타내고 저항곡선의 기울기는 크랙비에 따라 증가하였다. 3) Rice가 제안한 방법으로 [SS41의 J 하(1C)의 평균값은 모재는 22.8kgf/mm, 균질화 처리재는 24.7kgf/mm, 연화처리재는 26.9kgf/mm를 얻었다

• 한국자동차공학회논문집
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• 제7권8호
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• pp.91-98
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• 1999

This paper describes the air flow characteristics inside the throttle valve. Tow-dimensional steady incompressible Navier-Strokes equation are solved numerically with embedding the conceopt of the artificial compressibility and adopting the Baldwin-Lomax turbulence model. With varying the valve opening angles(the Reynolds number )such as 15$^{\circ}$(5000) , 45$^{\circ}$(3000) , 75$^{\circ}$(7000) and 90$^{\circ}$(10000), respectively. tow cases, with a valve shaft and without one, are analysed. The pressure loss between the entrance and exit is severe at 15$^{\circ}$, 100 times as larger as that of 90$^{\circ}$ case, which also depends much on the existece of the valve shaft. The counter rotating vortices are formed over the valve plate with the shaft at only 75$^{\circ}$. They are smally and very large scale in front and back of the valve shaft , respectively. The velocity profiles of 15$^{\circ}$ and 90$^{\circ}$ at the exit are almost symmetric to the horizontal center line, however, the symmetricity is no longer maintained at 45$^{\circ}$ and 75$^{\circ}$ , and in addition, the flow at 75$^{\circ}$ is enforced a lot below center line. The pressure distribution on the walls is largely changed near the valve shaft, and its magnitude becomes great as the valve angle decreases.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2008년도 춘계학술대회 논문집
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• pp.1903-1908
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• 2008

This paper presents a characteristics of linear induction motor considering airgap variation for railway transit in order to achieve high performance of the vehicle. The operating principle of a LIM(Linear induction motor) is identical to a rotary induction motor. Space-time variant magnetic fields are generated by the primary part across the airgap and induce the electro-motive force(EMF) in the secondary part, a conducting sheet. This EMF generates the eddy currents, which interact with the airgap flux and so produce the thrust force known as Loren's force. Even though the operating principal is exactly same as a rotary motor, the linear motor has a finite length of the primary or secondary parts and it causes static and dynamic end-effect which is the discontinuous airgap flux phenomenon. This end-effect causes the deterioration of the system performance, especially in high-speed operation. Another problem is that construction tolerance restricts the minimum airgap in order to prevent a collision between the primary part and the secondary reaction plate. More over, as the airgap length is getting smaller, the attraction force between the primary part and secondary parts is getting larger dramatically and the attraction force would be another friction against propulsion. Therefore, it is necessary to figure out the characteristics of linear induction motor considering airgap variation in order to achieve high performance of the vehicle. The dynamic model of LIM taking into account end-effects is derived. Then the modified mechanical load equation considering the effect of the attraction and thrust force according to the airgap variation is analyzed. The simulation results are presented to show the effect of the LIM according to the airgap variation.

• 한국강구조학회 논문집
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• 제12권3호통권46호
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• pp.291-302
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• 2000

복합적층 구조물에서 복합재료는 그 자체의 높은 강성, 강도와 내구성등의 특성을 갖고 있을 뿐 아니라, 구조물의 역학적 특성에 따라 얼마든지 재료의 특성을 합리적으로 구성하여 배치할 수 있는 매우 우수한 장점이 있다. 본 연구에서는 등분포로 재하된 복합적층경사판의 처짐에 관한 해석으로서 복합적층 경사판의 처짐을 나타내는 단일 4차 편미분방정식을 3개의 종속변수를 갖는 3원2차 연립방정식을 이용하여 해석하는 수치해석 법을 제시하였으며, 대칭 앵글-플라이 각도로 적층, 역대칭 앵글-플라이 각도로 적층, 비대칭 앵글-플라이 각도로 적층한 경우에 처짐과 단면력을 비교 검토하였다.

• 한국식품과학회지
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• 제33권2호
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• pp.221-225
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• 2001

꽃양배추색소추출액의 농도를 1-65%로 조절하여 그 유동 특성을 원뿔형 회전점도계를 사용하여 $20-50^{\circ}C$의 온도범위에서 조사하였다. 꽃양배추색소추출액의 유동특성은 단순 power law model을 사용하여 설명할 수 있었다. 실험범위 내에서 꽃양배추색소추출액의 유동거동지수(n)와 점조도지수(K)는 각각 0.841-0.998 및 $0.008-31.525\;Pa{\cdot}s^n$의 값을 나타냈다. 겉보기점도의 온도의존성은 Arrhenius식에 의해 결정할 수 있었으며, 활성화에너지는 용액의 농도와 전단속도에 따라 9.36-52.48 kJ/mol의 값을 나타냈다. 전단속도 $100\;s^{-1}$에서 측정한 보기점도에 대한 용액의 농도와 온도의 영향을 다음과 같은 단일지수모델식으로 표시할 수 있었다; ${\ln}\;{\eta}_a\;=\;6.11\;-\;3103.94(1/T)\;-\;0.03C$.

• 대한조선학회지
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• 제14권1호
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• pp.1-10
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• 1977

The major objects of this report are to supplement data of natural frequencies of thin elastic rectangular plates to the available data, and to give an experimental verification for natural frequencies obtained by Rayleigh-Ritz method, the generation set of which are eigenfunctions of Euler beams. For the first object the following five models, for which data only for the fundamental mode or data only for square plates are available, are adopted; (1) two opposed edges are clamped and the other two opposed edges simply supported (C-C, S-S), (2) one edge is simply supported and the other three edges clamped (C-C, C-S), (3) one edge is free and the other three edges clamped (C-C, C-F), (4) two adjacent edges are clamped and the other two adjacent edges free (C-F, C-F). For the (C-C, S-S) model the frequency equation obtained with the mode shapes assumed as of a single trigonometric series is solved. And for the other four models Rayleigh-Ritz method taking eigenfunctions of Euler beams as the generating set is applied. The numerical examples are obtained up to the fourth, the fifth or the sixth order depending on the range of the aspect ratio (0.1-10.0). The number of terms in the generating set for Rayleigh-Ritz method is fifteen for all models. For the experiment three models made of 3.2mm thickness mild steel plate for general structure use were prepared in following size; $300mm{\times}600mm,\;600mm{\times}600mm\;and\;900mm{\times}600mm$. Their boundary conditions are made to fit (C-C, C-F) condition. From the experiment mechanical impedance curves based on the frequency response method were obtained together with phase relation diagrams. The experimental data are resulted in good conformity to calculated values.

• Journal of Welding and Joining
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• 제34권6호
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• pp.42-46
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• 2016

Hydrogen assisted cracking (HAC) is one of the most complicated problem in welding. Huge amount of studies have been done for decades. Based on them, various standards have been established to avoid HAC. But it is still a chronic problem in industrial field. It is well known that the main causes of the hydrogen crack are residual stress, crack susceptible micro structures and a certain critical level of hydrogen concentration. Even though the exact generating mechanism is unclear till today, it has been reported that the hydrogen level in the weld metal should be managed less than a certain amount to prevent it. Matsuda studied that the residual hydrogen level in the weld metal can be varied even if the initial hydrogen content is same. It is also insisted in this report that the residual hydrogen concentration is in stronger correlation with hydrogen crack than the initial hydrogen content. But, in practical point of view, the residual hydrogen is still hard to consider because measuring hydrogen level is time and cost consuming process. In this regard, numerical analysis is the only solution for considering the residual hydrogen content. Meanwhile, Takahashi showed the possibility of predicting the residual hydrogen by a rigorous FE analysis. But, few commercial software suitable for solving the weld metal hydrogen has been reported yet. In this study, two dimensional thermal - hydrogen coupled analysis was developed by using the commercial FE software MARC. Since the governing equation of the hydrogen diffusion is similar to the heat transfer, it is shown that the heat transfer FE analysis in association with hydrogen diffusion property can be used for hydrogen diffusion analysis. A series of simulation was performed to verify the accuracy of the model. For BOP (Bead-On-Plate) and the multi-pass butt welding simulations, remaining hydrogen contents in the weld metal is well matched with measurements which are referred from Kim and Masamitsu.

• 대한토목학회논문집
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• 제34권6호
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• pp.1667-1676
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• 2014

강합성 바닥판은 두 방향의 휨 강성이 다르기 때문에 직교이방성의 성질을 가진다. 강합성 바닥판의 휨 강성비는 활하중 모멘트에 영향을 미친다. 비충전 강합성 바닥판의 휨 강성비는 메인 베아링 바 간격과 직접적인 관계를 가지고 있어 메인 베아링 바 간격과 형상비 영향이 고려된 하중분배 계수식에 대한 연구가 필요한 것으로 판단된다. 본 연구에서는 휨 강성비를 고려하는 AASHTO LRFD Bridge Design Specification에 의한 비충전 강합성 바닥판의 활하중 모멘트를 평가하고 비충전 강합성 바닥판의 하중분배 계수식을 제안하고자 한다.

• 대한기계학회논문집B
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• 제35권11호
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• pp.1169-1176
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• 2011

액막류는 레이놀즈수 및 유동 안정성에 의해 파동이 없는 층류액막류, 파동을 동반한 층류 액막류 및 난류액막류로 구분된다. 파동액막류는 강한 비선형성에 의해 매우 복잡하여 기존에는 주로 실험적 연구가 진행되었다. 수치적 해석은 주로 파동이 없는 경우에 국한되었으며 여러 가지 자유표면 해석기법을 이용하여 평균액막두께를 예측하였다. 이 연구에서는 층류액막류의 파동현상을 레이놀즈수 20~1000 범위에서 수치해석하였다. 이 때, VOF 자유표면 해석기법에 기반한 여러 가지 수치방법을 비교 연구하였으며 평균액막두께, 파동속도 및 진폭을 실험결과와 비교하였다.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2008년도 동계학술발표대회 논문집
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• pp.286-291
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• 2008

Insulation of refrigerator with gasket material near door becomes the technical point at the aspect of heat loss and energy efficiency. Heat loss of refrigerator through the gasket is nearly 30%. In this paper, quantitative evaluation method of heat loss through gasket in established suggest the method for the improvement of heat loss. To analyze the heat transfer, we have used the common software Fluent that is used to CFD. Because of using the convection coefficient of heat transfer, we have solved only the equation of energy for heat transfer. As a result, we have known that heat loss flows through the heat flux vector and that the heat gathered out of the outside iron plate is transferred inner part through the gasket and ABS, etc. Through the result of the numerical simulation that use sub-gasket, we have known that we are able to reduce the heat loss about $20{\sim}40%$. when we applied that sub-gasket on a real refrigerator, the power consumption had reduced about 4.76%. In addition, when we applied a more improved sub-gasket on a real refrigerator and measured the power of the refrigerator the power consumption does reduce about 3% and we will try to apply the improved sub-gasket on a new models of refrigerator.